1. Field of the Invention
The invention relates to land vehicles, wheels and axles. More specifically, the invention is an attachment to the wheels of a vehicle for giving traction to the tires in conditions of mud, snow, or ice in the vehicle's path.
2. Description of the Prior Art
Land vehicles have long had traction problems when weather conditions made road surfaces slippery, for example muddy or snow and ice covered. Conventional vehicles such as cars, trucks, busses, and tractors ride on round tires that depend on tread design to provide traction over slippery surfaces, while unconventional vehicles such as earth moving equipment are often supplied with belt-style tread. The present invention relates to conventional vehicles, hereinafter referred to as cars.
Prior art devices to provide traction to cars traveling over slippery surfaces have included such well known items as tire chains and studded tires. Both of these traction giving means are known to work well, but each has disadvantages. Tire chains are difficult to put on the tires and severely limit the speed of the car. In addition, the motorist often must install the chains while his car is in deep snow and the weather is cold, making the job messy and unpleasant. The motorist must place the chains on the ground, drive over them, and manually wrap the chain around the tire and fasten links together. This operation not only spreads snow or mud over the motorist, but requires that his car be able to move or that he jack up the wheels in order to bring the chain under the wheels. This great inconvenience is a major problem with the use of tire chains.
Studded tires provide improved traction on hard, icy surfaces and do not require the motorist to do more than purchase the studded ties before use. Many states, however, limit or prohibit the use of studded tires because the studs wear highway surfaces at a rapid rate. The fact that the studs are constantly in contact with the road surface regardless of road and weather conditions is a disadvantage that may lead to studded tires being outlawed in all states in the future. Accordingly, there is a need for a traction device that is convenient to install and use when road conditions so require, and that will not be constantly wearing highway surfaces in non-slippery weather.
Some devices in the prior art provide extendable and retractable traction studs suited for use in mud, for example on tractor wheels. U.S. Pat. No. 965,681 to Bagnell and No. 1,537,491 to Palmer are representative of such art. Tires using such pawls or studs as in the cited patents have never been successful because the studs lack flexibility needed to withstand the distortion of modern pneumatic tires on cars traveling at high speed. Furthermore, attachments of the kind in the cited patents are unsuited to fit automobiles with fenders surrounding much of the wheel well. In addition, such attachments lack the strength to provide friction against the ground.
Another severe problem with retractable studs is that the studs transmit road vibration and stress directly to their own hub, which is attached to the side of the regular car wheel. The full downward force of the studs against the road is thus transmitted through the union of the stud wheel hub and regular wheel, the connection being perpendicular to the plane of the rotation of the stud wheel. This arrangement is mechanically undesireable because of the relatively great stresses that can be transmitted to the union of the regular and stud wheels, and alternatively, because of the relatively small amount of traction giving force that the stud wheel hub can be expected to support. The present invention overcomes these and other problems seen in the prior art.